Summary of Invertebrate Density and Cerithium Size Distribution from the NURC Keyswide Cruise 1995

Prepared by

James A. Bohnsack and Tracey Baynes

Reef Resources Team Southeast Fisheries Science Center National Marine Fisheries Service 75 Virginia Beach Dr. Miami, 33149

MIA-96/97-14 Summary of Invertebrate Density and Cerithium Size Distribution from the NURC Keyswide Cruise 1995

James A. Bohnsack and Tracey Baynes

Introduction

The National Unsersea Research Center (NURC) sponsored a Keyswide survey in 1995 during which Dr. Baynes collected invertebrates from 0.25m' quadrats on reefs visited during two legs of the cruise. Data from her,final report (Appendix A) is presented in new figures 1 and 2. This report summarizes significant findings.

Methods

Mobile macro-invertebrates were collected from visual inspections of 14 to 15 0.25 m^ quadrats positioned randomly along transects at each reef site.

Results Compared to the rest of the Keys, significantly increased densities of hermit and Cerithium gastropods were found in the western Keys from Congrove Shoal to the Dry Tortugas (Fig. 1). There appears to be no significant relationship between either hermit density or cerith density and invertivore fish density (Figure 1). The gastropod C. litterat dominated the mollusks collected. Its size distribution in the western Keys varied greatly between reefs (Fig. 2): the Cosgrove population exhibited a high porpoprtion of small (young) individuals, the Tortugas Bank population exhibited a high proportion of large (adult) individuals, and the Pulaski Shoal population exhibited a relatively uniform size distribution. Causes of this pattern are unknown.

Figure Captions

Figure 1. Summary of invertebrate and invertivore fish distributions from the 1995 NURC Keyswide Cruise. Figure 2. Cerethium. Keyswide spatial distribution and size distribution from three reefs.

Key to Codes:

FR Fowey Rock SB Sombrero Reef TR Triumph Reef LK Looe Key Reef AJ Ajax Reef SK Sand Key Reef .CF Carysfort Reef CS Cosgrove Shoal PK Pickles Reef TB Tortugas Bank TN Tennessee Reef PS Pulaski Schoal Keyswide Cruisei 1995 Cerith Density (no./m2) Density (no./m2) 60 ^- - 12

10 40

s 30 6 20 4

10 2

0 M,-- 0 FR TR AJ CF PK TN SO LK SK CS TO PS FR TR Ai CF PK TN SO LK SK CS TO PS Study Sites (NE to SW) Study Sites (NE to SW)

Sea Urchin Density (no./m2) Invertivore Fish Density (no./sample) I 30

25 0.8

os is 0.4 10

0.2 no da ta

0 0 FIR TR Ai CF PK TN SO LK SK CS TO PS FR TR AJ CF PK TN SO LK SK CS TO PS Study Sites (NE to SW) Study Sites (NE to SW) Cerithium Spatial and Size Distribution 1995 Cerithium Distribution Cosgrove Shoal

Cerith Density (no./m2) No. of C. litteratum 50 30 F -- - - -

25 40

20 30 16 20 10

10 5

0 FA ^ ^ - m ^ mm oil i FR TR AJ CF PK TN SB LK SK CS TB PS 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 8 3.4 3.8 Study Sites (NE to SW) Length (cm)

Pulaski Shoal Tortugas Bank

No. of C. litteraturn No. of C. litteratum 30 30

26 26

20 20

16 is

10 10

6 5 1 JUE^ t1i F 71 ^-] 0.8 1 1.2 1.4 1.0 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 Length (cm) Length (cm) Af^oen d i',)(

Amphipod Collections and Gastropod Surveys: KeysWide Cruise (Aug. and Sept., 1995)

PI: Tracy W. Baynes Affiliation: Southeast Fisheries Science Center, Miami, Florida Date: 6/11/96

Macro-mverLebrate grazers (gastropods, urchins, and hermit crabs) were surveyed, and amplupods and gastropods were collected from deep reefs (water depths of 50-60 fL) throughout the Keys and Dry Tortugas during 2 summer cruim, from August 18th to 27th and from September 18th to 24th, 1995.

A survey of mobile inwro-invertebrate grazers was conducted by visual inspection of 14-15 0.25m2 quadrats positioned randomly or haphazardly along trarisects of each reef site. I use the term "grazers" to refer to organisms that ingest sessile biota, whether it be algae or sessile invertebrates. Gastropods were identified to . Survey/collection locations, gastropod species identifications, and numbers of gastropods, hermit crabs, and urchins surveyed per reef site are given in Table 1. The number of Ca-jWum and hermit crabs per 3.5-3.75 m2 of sampled reef surface is plotted for each reef site in Figure I a and I b, respectively. A majority of the censused hermit crabs were utilizing Ca-,rikh,.47m shells. The 3 southern-most sites (Cosgrove Shoal, Tortugas Bank, and Pulaski Shoal) edfibited noticeably higher densities of both OriMium spp. and hermit crabs. There appears to be no correlation between the density of fish species known to consume mobile macro-invertebrates (Fig. 2: obtained from Jim Bolmsack's reef fish surveys) and the density of CariMium or hermit crabs. was by far the most abundant mobile macro-invertebrate grazer encountered. The size distribution of the individuals surveyed at Cosgrove Shoal, Tortugas Bank, and Pulaski Shoal are plotted in Figures 3a, b, and c. Both the Cosgrove and Tortugas Bank populations exhibited skewed size distributions, with the Cosgrove population exhibiting a high porportion of small (young) individuals (Fig. 3a), and the Tortugas Bank population exhibiting a high proportion of large (adult) individuals (Fig. 3b). The Pulaski Shoal population exhibited a relatively uniform size distribution (Fig. 3c). Ile gastropods collected during the first 2 legs of the Keyswide Cruise are in the possession of Dr. Jim Bohnsack at the Southeast Fisheries Science Center in Miami, Florida.

Amphipods are found in high abundance on and around reefs, and am an important link in the food web of tropical benthic communities, both as grazers and scavengers of the benthos and as a food source for many reef fish. Their high abundance, trophic importance, site specificity, and sensitivity to a variety of pollutants points to their potential use as indicator species of stress on the reef (Thomas, 1993). Very little is known about the relative abundance and distribution of amphipod species throughout the Keys. Benthic infaunal amphipGds were collected on the first two legs of the Keyswide Cruise in order to obtain a first glimpse of the species composition and abundance throughout the reef tract. The collection and processing techniques utilized were developed by Dr. Jim Thomas. Each sample was obtained by dragging a heavy-duty 2-gallon plastic bag through the upper layer of sediment (approximately 1/2 inch deep) over a distance of about I meter. The bag was then closed off with a tie wrap, brought to the surface, and emptied intoabucket. The amphipods were separated from the sediment by a process which traps the amphipods in a surface film. The amphipods were then gendy poured off into a 0.5-1 mm mesh sieve and rinsed into a glass vial for preservation and storage. At this time, the amphipods from each bag have been separated out from the other micro-crustaceans and material collected on the mesh sieves. The species have not yet been identified. The amphipod samples are in the possession of Dr. Jim Bohnsack at the Southeast Fisheries Science Center in Miami, Florida. Reference:

Thomas, J.D. 1993. Biological monitoring and tropical biodiversity in marine environments: a critique with recommendations and comments on the use of amphipods as bioindicators. I Nat. Hist. 27: 795-806. TABLE I

Date Collection Site # of Quadrats Gastropod Spp. # Surveye # of Ceriths # of Hermit Crab # of Urch 8/19 Triumph 15 0 0 2 3 8/20 Pickles 14 Ctr,kh.iVM&&MtVM 7 7 2 1 8/21 Carysfort 15 C liMI-atum I 1 1 0 8/22 Sand Key 14 C AttAxamm 7 7 3 0 8/23 Cosgrove Shoat 15 C II&tMIUM tA 114 23 1 Aho-affodulos., I 8/24 Tortugas Bank 15 C I,&drdwM 79 85 37 0 ca-Athiam,wxatum 4 Orkhivm eburweam I cerithium,ewwatcum I M Bod,11CM, I ^a,16wmlllboc^aawm 1 8/25 Sombrero 15 C Itatramm 10 12 2 0 C ti^zwweum 2 2 ,phila abbre w;rta 2 Af -Oodulosa I 'VOffCbOj-?&rVS "jvhvesoaicvs I 8126 Tennessee 15 C MterIMM 3 3, 8 0 8/27 Fowey 15 C h&ej-ajvm 6 13 1 0 C e6w-weum 7 AWeIM,niqpffcvIq I FrO-40M MOOQ^a= I 9/18 Ajax 15 C I,&trdwM 3 3 3 0 Lda?us CwyMfffVS 1 9/19 Looe Key is C likArRIUM 11 12 15 0 C e&waeum Af 0A)UMS CO'-A1ffO,PAiI&C4wrib&ew I Car.41M)PAila sca.ld"forinfIr I 9/20 Pulaski Shoal 15 C Arterwwm 146 152 34 C eburffeam 4 C atratum 1 Cgurzigicam I Af -aodulaw 2 C"S"Spira cubwa I Mvre-t-mwqr6yM I .Airssadysalbas I

INVERTEBRATE PREDATOR DENSrTY I

40

a 30 Ui IL

20

z LLI Q to

0 1 2 3 4 5 6 7 9 10 1 11 12 REEF

#OF REEF # REEF,t. N SAMPLES REEF # DENSITY 8 LOOE KEY 193 12 1 16.375 4 CARYSFO 118 11 2 10.16667 9 SAND. 75 9 3 8.166667 2 TRIUMPH 122 12 4 10.72727 3 AJAX 98 12 5 13.1 12 PULASKI 317 11 6 14.19048 11 TORTUGA 99 9 7 0 10 COSGROV 49 10 8 16.08333 6 TENN 298 21 9 8.333333 1 FOWE 131 8 10 4.9 5 PICKLES 131 10 11 11 7 SOMBRERO 0 12 28.81818

SPECIES COMMONNAME SPECIES COMMONNAME Anisotremus surinamensis Black margate Haemulon macrostom^-M Tr ish grunt Anisotremus virginicus Porldish Heemulon melanurum Cottonvvick Aulostomus maculatus Trumpetfish Haemulon parra Sailor's choice bajonado Jofthead porgy Haemulon plumied White grunt Calamus calamus Saucereye porgy Haemulon sciurus Bluestriped grunt Dasyaba americans Southern stingray Holocentrus adiscensionis Squirrelfish Epinephelus adscensionis Rock hind Holocentrus marianus Longjaw squirrelfish Epinephelus cruentatus Graysby Holocentrus rufus Longspine squirrelfish Epinephelus fulvus Coney Lachnolaimus ma)dmus Hogfish Epinephelus guttatus Red hind Lutjanus analis Mutton snapper Epinephelus mono Red grouper Lutanus apodus Schoolmaster Epinephelus striatus Nassau grouper Lu1janus griseus Gray snapper Ginglymostoma cirraturn Nurse shark Lutjanusjocu Dog snapper Haemulon aurolineaturn Tomtate Lutjanus mahogoni Mahoganysnapper Haemulon carbonarium Caesar grunt Luqanus synagris Lane snapper Haemulon chrysargyreurn Smailmouth grunt Myeteroperca bonaci Black grouper Haemulon flavolineaturn French grunt Rypticus saponaceus Greater soapfish Urolophusjamaicensis Yellow stingray a Cosgrove Shoal OL. 30

6 20

U '41- 10

a

0 0.8 1 1.2 1.41.6 1.8 2 2.22.4Z6 2.8 3 1.2 Length ("^

4

Tortugas Bank 60 30

20 ,...a06

10

0 0.8 1 1 -2 1 -z I -E 1.8 2 2.2Zz?-E2.8 3 3.23.4 Length (c),,)

Pulaski Shoal C^. 30

6 20 ^

N 10^

0 0.8 1 1.'. 1.4 1.f 1.8 2 2."2.-2.f 2.8 3 3."3.,3.6 Length Cc-^)